US 7682017 B2
Methods and apparatus include a handheld printer manipulated back and forth by an operator during use to print an image. An inkjet printhead of the printer has a plurality of fluid firing actuators arranged in a substantial column. A controller communicates with the printhead to identify active actuators given to fire at a particular time during use to print the image. However, to prevent unsightly print quality from occurring during overlapping adjacent print swaths, for example, certain of the identified actuators are prevented from firing. Especially, actuators in the column further from a center of the column fire less frequently than those closer to the center. A position sensor is also used to locate the printhead relative to the image. The controller correlates the position to the printhead and actuators and fires the active actuators or not.
1. A handheld printer, comprising:
an inkjet printhead having a plurality of fluid firing actuators; and
a controller communicating with the printhead to identify ones of the actuators requiring firing to print an image and to prevent firing some of the identified ones of the actuators to avoid print banding during use; wherein the controller correlates the location of the printhead to the image and proportions the actuators in the column further from a center of the column to fire less frequently than the actuators closer to the center.
2. The handheld printer of
3. The handheld printer of
4. The handheld printer of
5. The handheld printer of
6. The handheld printer of
7. The handheld printer of
8. A handheld printer to be manipulated back and forth by an operator during use to print an image, comprising:
a hand maneuverable housing for an operator;
an inkjet printhead in the housing having a plurality of fluid firing actuators arranged in a substantial column;
a controller communicating with the printhead to cause firing or not of ones of the actuators during use when adjacent print swaths of the housing overlap;
a position sensor communicating with the controller to provide a location of the printhead during use,
wherein the controller correlates the location of the printhead to the image and proportions the actuators in the column further from a center of the column to fire less frequently than others of the actuators closer to the center.
9. The handheld printer of
10. The handheld printer of
11. The handheld printer of
12. A method of printing an image with a handheld printer having an inkjet printhead in a housing, comprising:
determining whether fluid firing actuators of the printhead should fire in printing the image; and
if the actuators should fire, identifying ones of the actuators to avoid firing based on a position in a column of fluid firing actuators, wherein the controller correlates the location of the printhead to the image and proportions the actuators in the column further from a center of the column to fire less frequently than the actuators closer to the center.
13. The method of
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Generally, the present invention relates to handheld printers. Particularly, it relates to improving print quality in handheld printers of the type able to print in random motion patterns. In one aspect, stitching together overlapping print swaths is contemplated. In another, dithering per edges of columns of nozzles of an inkjet printhead is contemplated. Still other aspects relate to methods and structures for accomplishing same.
As is known, handheld printers afford mobile convenience to users. Unlike their immobile or stationary counterparts, however, users determine the path of a given swath of printing. In some instances, this includes random movement over a substrate. In others, it includes back-and-forth movement attempting to simulate a stationary printer.
A common problem with handheld printers is poor alignment between adjacent swaths of print because position of the print element is often less accurate than with other types of printer. Alignment errors usually result in noticeable defects in the print. The most common print defects are called “print banding” and include both dark bands and white bands at the boundary between swaths where ink drops at the edge of a swath are printed too close or too far from drops in the adjacent print swath. Another category of print banding is a directional effect similar to the banded appearance of mowed glass when adjacent swaths are cut in different directions. These print banding defects may appear with other serial printers, but the defects can be minimized by printing a dithered image in multiple passes over the paper. With a handprinter, print banding is a problem because alignment errors are more likely, and requiring multiple passes is an unaccepted demand on the operator.
Another common defect with handprinting is a gap or void in the print where the operator fails to pass the print element over that portion of the page. If detected, the operator can repair the void by moving the print element back over that area so the missing content can be printed. With a handprinter, positional errors accumulate during the page, so voids that are not repaired promptly may have significant print banding where the area printed in repair is misaligned with the adjacent areas.
Accordingly, there exists a need in the art for robust, multi-directional and random printing handheld printers having improved print quality. Naturally, any improvements should further contemplate good engineering practices, such as relative inexpensiveness, stability, low complexity, ease of manufacturing, etc.
The above-mentioned and other problems become solved by applying the principles and teachings associated with the hereinafter described handheld printers that minimize printing defects. Specifically, methods and apparatus contemplate handheld printers manipulated randomly or predictably over a substrate on which an image is printed. In this regard, the printer examines which fluid firing actuators of an inkjet printhead in the printer are active to fire. From those, some are intentionally prevented from firing to create a dithered image having improved print quality, especially in contemplation of overlapped adjacent printing swaths.
With a handheld printer, the operator must overlap swaths to avoid voids or print gaps. Since swaths must overlap to some extent, this invention takes advantage of that requirement to implement selective printing or dithering in the overlap zone. Doing so places no additional demands on the operator as might if (for example) full coverage multiple passes of the printer were required to reduce banding.
In one aspect, the handheld printer includes a position sensor, a controller and a printhead. The sensor provides the location of the printhead and the controller correlates the actuators of the printhead to a to-be-printed image. In turn, the printhead has a plurality of fluid firing actuators arranged in a substantial column. The controller communicates with the printhead to identify active actuators given to fire during use to print the image. However, to prevent unsightly print quality from occurring during adjacent print swaths, for example, certain of the identified actuators are prevented from firing. Especially, actuators in the column further from a center of the column fire less frequently than those closer to the center.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in the description which follows, and in part will become apparent to those of ordinary skill in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims.
The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:
In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention and like numerals represent like details in the various figures. Also, it is to be understood that other embodiments may be utilized and that process, mechanical, electrical and/or other changes may be made without departing from the scope of the present invention. In accordance with the present invention, a handheld printer that minimizes printing defects is hereafter described.
With reference to
Adhered to one surface 118 of the housing 112 is a portion 119 of a flexible circuit, especially a tape automated bond (TAB) circuit 120. At 121, another portion 121 is adhered to another surface 122. In this embodiment, the two surfaces 118, 122 are arranged perpendicularly to one another about an edge 123 of the housing. Electrically, the TAB circuit 120 supports a plurality of input/output (I/O) connectors 124 for connecting an actuator chip 125, also known as a heater chip, to the handheld printer during use. Pluralities of electrical conductors 126 exist on the TAB circuit to electrically connect and short the I/O connectors 124 to the input terminals (bond pads 128) of the actuator chip 125 and skilled artisans know various techniques for facilitating this. In an exemplary embodiment, the TAB circuit is a polyimide material and the electrical conductors and connectors are copper or aluminum-copper. For simplicity,
At 132, the actuator chip 125 contains at least one ink via (alternatively reference numeral 580 in
With reference to
Among other things, the controller 22 also includes a stored to-be-printed representation of an image 32. In turn, it correlates the position of the printhead, especially individual actuators, to the image. It then prints the image with ink 35 on the substrate 16 according to the image pattern 36 in the pixels 38. A has-been-printed image 34 may also be stored or accessed by the controller to keep track of future printing and to determine whether the image has been printed completely or not. In structure, the controller may embody an ASIC, discrete IC chips, firmware, software, a microprocessor, combinations thereof or the like.
In an alternate implementation, the to-be-printed image representation 32 is dynamically updated to remove pixels that have been printed so that the has-been printed information 34 is merged with the to-be-printed information.
To minimize print defects and improve print quality, the controller further identifies which fluid firing actuators of the printhead are active to fire in printing the image. From those, some are intentionally prevented from firing to create a dithered image having improved print quality, especially in contemplation of overlapped adjacent printing swaths. In one aspect, certain of the identified actuators are prevented from firing. Especially, actuators in the column of actuators further from a center of the column fire less frequently than those closer to the center.
Graphically, the actuator or nozzle number, from number 1 to some number n per a given column of fluid firing actuators 42, is laid adjacent the printing swath 41 to show image printing coverage in percent. As is seen, nozzle numbers further away from a center C yield lower coverage percent than do nozzle numbers closer to the center. In a preferred embodiment, this results because the terminally positioned actuators are fired less frequently than centrally positioned actuators. For instance, one embodiment contemplates that actuators with nozzle numbers 1 and n (e.g., actuators 51) fire only 1 out of 10 fire times per a given printing swath. In turn, actuators 2 and n−1 fire 2 out of 10 times, while actuators 3 and n−3 fire 3 out of 10 times and so on until nozzle numbers 10 and n−10 fire 10 out of 10 times. With reference to
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Finally, if the to-be-printed image is completely printed at step 316, the process ends. If not, the printer is moved at step 318 and repeated until eventually the entire to-be-printed image is rendered on the substrate. To ascertain this, it is preferred the controller 22 (
In still another embodiment,
In any embodiment, certain advantages of the invention over the prior art are readily apparent. For example, the invention at hand minimizes print banding and improves print quality. Less intuitively, whenever an operator using the handheld printer of the invention traverses visible voids in the image, the dithering of printing produces better quality. Also, because of simple logic in the apportioning of which active or to-be-fired actuators are prevented from being fired in a column of actuators, printing robustness is added while manufacturing costs are minimized.
Finally, one of ordinary skill in the art will recognize that additional embodiments are also possible without departing from the teachings of the present invention. This detailed description, and particularly the specific details of the exemplary embodiments disclosed herein, is given primarily for clarity of understanding, and no unnecessary limitations are to be imported, for modifications will become obvious to those skilled in the art upon reading this disclosure and may be made without departing from the spirit or scope of the invention. Relatively apparent modifications, of course, include combining the various features of one or more figures with the features of one or more of other figures.
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